As optical materials for liquid-crystal displays, among other uses, materials of low birefringence, small coefficient of photoelasticity, and high optical transparency are used. Moreover, in the case of materials for liquid displays, the production process involved makes it mandatory to use highly heat-resisting materials. As the raw materials satisfying these requirements, glass and the like have heretofore been employed.
While optical materials for liquid crystal displays, among other uses, are used in a thin film form or a fine tube or rod form in many instances, the recent market calls for the use of a thinner film form or a finer tube or rod form. However, the conventional material glass is brittle and, hence, the scope of its utility is self-limited under the circumstances.
As tough materials, high polymer materials are available but in the case of thermoplastic resin, for instance, introduction of an aromatic skeleton for expression of high heat resistance generally results in increased birefringence and increased coefficient of photoelasticity, so that it is difficult to reconcile high heat resistance with good optical properties. In the case of thermosetting resin, the thermosetting resins heretofore known are generally colored and, therefore, unsuited for optical use. Moreover, these resins generally have polarity and are unfavorable for expression of optical properties.
There has been proposed a curable composition comprising a compound having a carbon-carbon double bond, a compound containing a SiH group, and a hydrosilylation catalyst (e.g. Japanese Kokai Publication Hei-03-277645, Japanese Kokai Publication Hei-07-3030, Japanese Kokai Publication Hei-09-302095, Japanese Kokai Publication Hei-05-295270, Japanese Kokai Publication Hei-07-62103). The specific compositions thus proposed invariably provide for the satisfactory physical, thermal, and electrical characteristics attributable to the crosslinking reaction between the carbon-carbon double bond and the SiH group. However, since none are satisfactory enough in the aspect of optical transparency, these compositions are not suited for optical use and, hence, limited in industrial value.
A curable composition containing a triallyl isocyanurate as a component has also been proposed (Japanese Kokai Publication Sho-50-100, Japanese Kokai Publication Hei-09-291214). Among the specific compositions proposed, the cured artifact obtainable from the curable composition described in Japanese Kokai Publication Sho-50-100 has only a low glass transition temperature and is inadequate in heat resistance.